Apparatus for measuring velocity



Sept. 2, 19 52 R. A. RAMEY ET AL 2,603,860

APPARATUS FOR MEASURING VELOCITY Filed June 9, 1947 2 SHEETS+-SHEET lVOZTMETFI? I"; l: l

FORCE BALANCING SYSTE'M WJ I i llVVf/VTORS $05441 61 aaA MW, A Wet g ger/ 60mm,

dv' (L A r70'R/v y CURRENT SOURCE R. A. RAMEY ET AL APPARATUS FORMEASURING VELOCITY Sept. 2, 1952 2 SHEETS-SHEET 2 Filed June 9, 1947 i aM 5 w OOOtcuuu field emanating from =mventicn shown in l in theconducting Patented Sept. 2, 1952 APPARATUS Fen MEASURING TVELOCIT'Y- aRobert A Barney and Walter Seller,

,Cincinnati .Qhio

.Ae iieati a-nme 9,1947;"S'erialNoL153396" v The object or thisinyentidn-is methods and apparatus for measuring-1 the speed ofelectrically conducting systems byf the reaction means of detecting amagnetic field produced by the electric currents induced in saidconductin systems, which-in turnare produced by the relative velocity-ofthe systems 'andandthermagnetic the before-named apparatus. V 'A furtherobject of thisi-nvention is to provide metheds and apparatus formeasuring speed of *the; apparatus through a conducting fluid bytheforce reaction on parts of the apparatus pro-V duced by the electriccurrents induced in the fluid by the magnetic field emanating from theapparatus and the velocity of this apparatus- ;with respect tothisfiuid/A- still further Object of this invention is--to provide methods andapparatu's for 'measuring s peed of' the apparatus through a conductingfluid "by the voltage induced in'detector'coils in appa- --ratusproduced from a variable magnetic field coming fromthe circulatingcurrentsin the fluid produced by the variable magnetic field emanatingfro'mthe apparatus and the velocity of the apparatus with respect to theflu id.

'l h'e method and apparatus may best be understood by a reference tothe'- emb'odiinent of the 1 illustrates "a iveloc'imeter embodying ourinvention in which the pickup coils are constructed in thearrangement ofa figure eight for substantially balancing out all induced voltagesexistent in the velocimete'r system when the -;apparatus is stationary;Fig. 2 diagrammatically and schematically shows oneof the metho'ds forcompensating for varying resistivity of the mov- "ingconducting's'ystem, together --wi-th a method of supplying voltage andFig. 3 schematically shows one of the methods we employ forcorrectingth'e velocimeter system for resistivity changes fluid i'nwhich the velocimeter is used.-- g "Referring to the drawingsih detail;the magnetic velocimeter of our invention is intended *for installationbeneath the hull of a vessel-, and enclosed in a non-magneticstreamlined ousing depending from the've'ssel into the sea: Water theaccompanying drawings;

ac Claims, (circamai provide asmor'e fully explained in ourcopendingapplication Serial Number; 684,606, filed July 1-8;: 1946,

for-Method and Apparatus for Force Balance.

The force-balancing system is rep-resented at vI in Fig; 3 z and"includes displaceable "magnetic winding arranged in an intensemagneticfifi d emanating from an associated field structure, the windingbeing connected with a' circuit extending through required amplification.to an indicating device; i ig;? 1 shows an C. magneticvelocimeterembodying ourinvention using pickup coils '24 constructed as a figure:eight to determine the magni'tud'e of the velocity magneticfield,"that;is.. the

'field dueto-the cur-rent inducediin the moving conducting system.Exciting coil 18 is supplied with alternating current'Isa-through wiresl9 producingah exciting magnetic field whose directions are noted by thearrows along line "20.- -The electrical conducting system whose-speedrelatiye rto'fohe apparatus isrtoibe. measured passes the-coil fac'etcontinuously with its-velocity CirculatiPin'g electrical currents .10,with the instantaneous :directi'on's andpaths noted, are generatedainthe moving conducting system, producing a velocity magnetic held. withinstantaneous directions noted :by.= the arrows along'li'ne 121 andpropor- .tional to lithe indueedcurrents 'Ie, which are in turndirectlyeproportional to the velocityV and the current 1st and inverselyproportional to the :resistivity of the --moving conducting system.

Whenthe current 'Iactis magde'proportionalto the resistivity of themoving conducting system, the magnitude of the velocity magnetic fieldis 35 directly. :proportional to. the velocity. :V. The

- ured by'the voltage Ev itgenerates in; the pickup magnitude of-thevelocity magnetic afield is meascoi'ls2 4'.: The-winding-inthe form ofasfigure eight" of 1 these coils-v: 24, provides a convenient method forbalancing out the voltages which are generatedin the-pickup coils24'loy' the exciting magnetic fieldand by "the directly induced our- 7tests in the conductingsystem which is radiallysymmetricalgand-fordetecting the velocity mag- [re ect to ,xnasm ude buoppo in dltec w The advantage pi the figure of eightiwinding ,24

metr field, that-11s,, bilaterally symmetric "with will be a'p' rj eciate'd by considering the' e'a'se and "cefiicijencyj with which thevoltages may be'fbal- .anced turri by turn'where voltages ofon ly smallmag nitudeexist, The coils forming the figure :of eightgcirouitare notarranged to react upon vthemselves ceil -bycoil wheresubstantialrnagnitude of," voltage lmayex ist but the "balancing isperformed under conditions where voltages 0f coil might reasonablyinvolve the balancing of voltages of the order of magnitude of 1000volts so that the insulation problem is both expensive and difiicult.The space problem is also a major point of consideration as it isdesirable to have the energizing winding [8 as close to the conductingfiuid as possible. This is difiicult where the winding 24 would have tobe insulated against breakdown under conditions of very high voltages.However, with the figure of eight winding where the insulation isefiected turn by turn the insulation required is only that suflicient toinsulate terminal voltages of the order of the .voltage. of one turnwhich are less than a volt. I The figure of eight winding also has theadvantage of reducing circulating currents in the winding circuitarising from interwinding capacitance.

These circulating currents may be of substantial magnitude in theconventional coil but in the figure of eight winding used in ourinventionthis circulating current is reduced to a comparatively smallmagnitude. These circulating currents are undesirable as theynecessarily interfere with stability of the measuring circuit. Thefigure of eight winding serves to maintain these circulating currents ata value far below the minimum that can be achieved by balancing thesevoltages coil by coil instead of turn by turn as is eifected in ourinvention. We selected the figure of eight arrangement for itsubstantially balances out all induced voltages when the apparatus isstationary. Coils 24' and 24" are provided to accurately balance outthose voltages by adjusting current Ib in circuit 25. Measurement by avoltmeter of the voltage Ev from the pickup coils 24 at circuit 25 givesa reading which is calibrated in units of speed.

' In Fig. 2 one of the methods for compensating for varying resistivityof the moving conducting system is shown together with a method ofsupplying voltage of the operating frequency to the exciting coil.Electric power is supplied tothe system through transformer 21 andthetcurrent in the secondary system is rectified in tube 28 and filteredby condensers 29 and 30 and choke 3| providing a source of directvoltage. This voltage is controlled by the voltage on control tube 32and is applied to oscillator tubes 33- and 34 through transformer 35having tickler coils 36 and 31 magnetically coupled with primary coil 38and secondary coil 39 which connects to the exciting coil l8 of thevelocimeter. A resonating condenser M is connected across exciting coil[8.

When the D. C. voltage is applied to the oscillator tubes 33 and 34 theywill supply A. C. current to the velocimeter coil l8. The-amplitude ofthis A. C. current is proportional to the applied D. C. voltage.Magnetically couplied. to the velocimeter exciting coil 18 is coil 42whose voltage depends directly upon the current in the exciting coil l8.The output voltage of coil 42 is applied to the conductivity cell 43 andthe resistor 44 in series. Since the conductivity resistance of cell 43is made large relative to the resistance 44 the voltage across theresistance 44 i is proportional to the exciting current of theelectromagnetic velocimeter divided by the resistivity of the movingconducting system. The

j resonant or not.

voltage across resistor 44 is amplified by tube 45 and rectified by tube46 providing a D. C. voltage across resistor 41 and the shuntingcondenser 48 which voltage is applied to regulator tube 49 whichprovides the grid voltage for control tube 32. Constant voltage tube 50is used as a reference voltage for control tube 32 and constant voltagetube'Sl provides plate voltage for amplifiertube45."

The function of this system is to provide exciting current to theexciting coil i8 which is directly proportional to the resistivity ofthe associated moving conducting system. By holding the voltage acrossresistance 44 constant the ratio of exciting current to resistivity isheld constant and so they are always directly proportional.

To demonstrate the circuit operation assume the conductivity hasdecreased. The voltage across resistance 44 increases and is amplifiedin tube 45 and rectified and applied to the regulator tube 49 increasingits grid voltage and dropping its plate voltage and so dropping the gridvoltage of the control tube 32 and so decreasing the D. C. voltageapplied to the oscillator and also the current supplied to the excitingcoil [3 dropping the voltage across resistance 44 to its original value.

Since the output of the pickup coils 24 (shown in Fig. 1) is directlyproportional to the velocity V and the current Ian and inverselyproportional to theresistivity, then, since Inc has been made to varydirectly with the resistivity (constant ratio), theoutput voltage of thepickup coils 24 is proportional only to the velocity V. v In Fig. 3 wehave shown a method for correcting for resistivity changes in conductingfield. The output current of the force balancing system I is sentthrough a conductivity cell 54 and the voltage across this cell is readon voltmeter 55 which automatically provides a compensated reading.Since the output current of the force balancing system is proportionalto the velocity dividedby the resistivity and the output voltage of theconductivity cell 541s proportional to the resistivity of the conductortimes the output current of the force balancing current, a simplemultiplication shows that the resistivity efiects are immediatelycancelled and the voltmeter reading depends entirely upon the velocity;An A. C. type of force balancing system is used when this type'ofconductivity measurement is'used.

The general problem to which our invention has been addressed is tomeasure the speed of the electrically conducting system by theinteraction on measurement apparatus of electrical currents generated inthe moving conducting system by the conducting system's velocityrelative to a magnetic field emanating from the measurement apparatus.In the example illustratedthis' interaction has been measured by theelectromotive force generated in a pickup coil (Fig. 1).

The specific size or shape of exciting. coils, pickup coils, andferromagnetic cores is not critical and we'do not intend to limit thegenerality oi the solution of this problem to theparticular apparatusand circuits illustrated. For example the pickup coils 24 may be woundin the shape shown or as/or more symmetrically located coils coactingwith the exciting field balanced either by bucking the coil outputvoltages due to the exciting field, orby locating the pickup coils overthe exciting coils in such aposition as to make the vector sum of theexciting fiux through the coil zero. The pickup coils may be 'Methods ofbalancing'out the efiects in the h measurement apparatus are varied 'dueto the exciting magnetic fleldisuc'h as by introducing the balancingcoil, as in Fig. 1.

S fiorrfection forresistivity changes, as illustrated ilireinfisnot.intended .to limit; the generalityitof this application sinceit isrecognized tnati-any method of measuring resistivity and properlycorrecting the final reading by use of the obtained data, eithercontinuously or intermittently may be used in making velocitymeasurements whose accuracy depends upon the method and apparatus used.The two methods shown in Fig. 2 and Fig. 3 are of the continuous types.

While we have described our invention in cersurface of the electricallyconducting fluid I through which said body moves, means for exciting oneof said windings for establishing a magnetic field of force in theelectrically conducting fluid and producing thereby a reactionarymagnetic field operative to energize the other of said windings, ameasuring system for detecting the reactionary effect upon said lastmentioned winding, an observing device connected with said measuringsystem, said last-named winding being arranged substantially in the formof a figure eight with transverse portions thereof extendingsubstantially diametrically of said first mentioned winding, a coilelectrically coupled with each transverse portion of said figure ofeight winding, a series circuit including said coils, and a source ofcurrent for compensating for voltage unbalance in said figure of eightwinding.

2. Means for electrically measuring the velocity of a body movingthrough an electrically conducting fluid comprising a pair ofinductively related electrical windings disposed below the surface ofthe electrically conducting fluid through which said body moves, meansfor exciting one of said windings for establishing a magnetic field offorce in the electrically conducting fluid and producing thereby areactionary magnetic field operative to energize the other of saidwindings, a measuring system for detecting the reactionary effect uponsaid last mentioned winding, an observing device connected with saidmeasuring system, said last-named Winding being arranged substantiallyin the form of a figure eight with transverse portions thereof extendingsubstantially diametrically of said first mentioned winding, a pair ofcompensating coils electromagnetically coupled with each lobe of saidfigure of eight winding and electrically connected in series and acurrent source connected in said series circuit for electricallybalancing said wind- 3. Means for electrically measuring the velocity ofa. body moving through an electrically conducting fluid comprising apair of inductively related electrical windings disposed below thesurface of the electrically conducting fluid through which said bodymoves, means for exciting one of said windings for establishing amagnetic field of force in the electrically cond tirig fiuieasuprcsucingtherebya reactionary field operative: to energize theenthersaid: last mentioned winding havihg the form of a r-figure of eight in aplane substantially parallel to the plane of the other winding, ameasuringsystem for detecting the reactionary effect u o id ast mentiqner win ing, an observing device connected gwith said measuring system,and means coupled with each lobe of said figure of eight winding andelectrically connected in series for compensating for voltage unbalancetherein.

'4. Means for electrically measuring the velocity of'a body movingthrough an electrically conducting fluid comprising a pair ofinductively related electrical windings disposed below the surface ofthe electrically conducting fluid through which said body moves, meansfor exciting one of said windings for establishing a magnetic field offorce in the electrically conducting fluid and producing thereby areactionary magnetic field operative to energize the other of saidwindings, said last mentioned winding having the form of a figure ofeight in a plane substantially parallel to the plane of the otherwinding, a measuring system for detecting the reactionary eifect uponsaid last mentioned winding, an observing device connected with saidmeasuring system, and electromagnetic means magnetically coupled witheach of the lobes of said figure of eight winding for compensating forvoltage unbalance therein.

5. Means for electrically measuring the velocity of a body movingthrough an electrically conducting fluid comprising a pair ofinductively related electrical windings disposed below the surface ofthe electrically conducting fluid through which said body moves, meansfor exciting one of said windings for establishing a magnetic field offorce in the electrically conducting fluid and producing thereby areactionary magnetic field operative to energize the other of saidwindings, said last mentioned windin having the form of a figure ofeight in a plane substantially parallel to the plane of the otherwinding, a measuring system for detecting the reactionary effect uponsaid last mentioned winding, an observing device connected with saidmeasuring system, and means disposed coplanar with the plane of eachlobe of the figure of eight winding and individually coupled with therespective lobes for compensating for voltage unbalance therein.

6. Means for electrically measuring the velocity of a body movingthrough an electrically conducting fluid comprising a pair ofinductively related electrical windings disposed below the surface ofthe electrically conducting fluid through which said body moves, meansfor exciting one of said windings for establishing a magnetic field offorce in the electrically conducting fluid and producing thereby areactionary magnetic field operative to energize the other of saidwindings, said last mentioned winding having the form of a figure ofeightin a plane substantially parallel to the plane of the otherwinding, a measuring system for detecting the reactionary effect uponsaid last mentioned winding, an observing device connected with said 9f:eight winding and being electrically excited V UNITED STATES PAYI'ENTS'fe l-cgmpensating for voltage imbalance therein. Number a,me; l, 'pDat1,11; 1 i; i O M 1,249,530- Smith et al.' Deb.v11,v1917 L WAL LL -I- 52,149,347 Kolin Ma'r.-7;1939

. I. VREFE-RENCEVS CI llehdg gl; al Jan}. 27,

